• 한국항공운항학회지
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• 제19권1호
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• pp.1-6
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• 2011

The free-wing tilt-body aircraft is researched in the flight performance characteristics such as short take-off and landing capability, and reduced sensitivity to gust and center of gravity (CG) change. Due to the main wing separating from the fuselage, the high tiltable empennage, and the stub-wing strongly influencing from the propeller wake, the resulting vehicle aerodynamics and flight dynamics are quite different from those of a conventional fixed-wing aircraft. Using the governing flight dynamics model was studied previously, all of speed and body tilt angle is simulated to determine the flight envelope by a non-linear 3-DOF flight simulation analysis. Though flight performance and trimmability are studied, the flight model of free-wing tilt-body aircraft is to reduce the hidden risk and to achieve the successful flight test. It is analyzed the flight characteristics that distinguishes free-wing tilt-body aircraft from the conventional aircraft.

• Wind and Structures
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• 제11권2호
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• pp.137-152
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• 2008

This paper discusses engineering aspects of the rear-flank downdraft that was recorded near Lubbock, Texas on 4 June 2002, and produced a gust wind speed nearly equal to the design value (50-year return period) for the region. The general characteristics of the storm, and the decomposition of the time histories into deterministic 'running mean' and random turbulence components are discussed. The fluctuating wind speeds generated by the event can be represented as a dominant low-frequency 'running mean' with superimposed random turbulence of higher frequencies. Spectral and correlation characteristics of the residual turbulence are found to be similar to those of high-frequency turbulence in boundary-layer winds. However, the low-frequency components in the running-mean wind speeds are spatially homogeneous, in contrast to the low-frequency turbulence found in synoptic boundary-layer winds. With respect to transmission line design, this results in significantly higher 'span reduction factors'.

• 한국생물환경조절학회:학술대회논문집
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• 한국생물환경조절학회 1994년도 봄 심포지움 및 학술논문발표요지
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• pp.111-114
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• 1994

상대적으로 사하중에 비해서 활하중 영향이 민감하게 작용하는 농업시설의 경우, 경제성 및 안정성에 근거한 구조설계를 위해서는 활하중의 결정요인의 정확한 분석을 통한 합리적인 설계하중의 산정이 필요하다. 단위적설 중량은 적설심에 따른 구분을 사용한다면 대부분 적설심 50cm 이하의 범위에 속하기 때문에 일률적으로 1.0kg/cm/$m^2$ 을 적용해야 하지만, 정확한 적설하중 산정을 위해서 기온에 따른 단위 적설중량의 변화를 분석할 필요가 있다. (중략)

• Wind and Structures
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• 제5권2_3_4호
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• pp.151-164
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• 2002

Predictions of the pedestrian level wind speeds for the downtown area of Auckland that have been obtained by wind tunnel and computational fluid dynamic (CFD) modelling are presented. The wind tunnel method involves the observation of erosion patterns as the wind speed is progressively increased. The computational solutions are mean flow calculations, which were obtained by using the finite volume code PHOENICS and the $k-{\varepsilon}$ turbulence model. The results for a variety of wind directions are compared, and it is observed that while the patterns are similar there are noticeable differences. A possible explanation for these differences arises because the tunnel prediction technique is sensitivity to gust wind speeds while the CFD method predicts mean wind speeds. It is shown that in many cases the computational model indicates high mean wind speeds near the corner of a building while the erosion patterns are consistent with eddies being shed from the edge of the building and swept downstream.

• Wind and Structures
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• 제19권5호
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• pp.541-563
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• 2014

This paper investigates the topographic effects on wind characteristics over hilly terrain, based on wind data recorded at a number of meteorological stations in or near complex terrain. The multiply data sources allow a more detailed investigation of the flow field than is normally possible. Vertical profiles of mean and turbulent wind components from a Sodar profiler were presented and then modeled as functions of height and wind speed. The correlations between longitudinal and vertical wind components were discussed. The phenomena of flow separation and generation of vortices were observed. The distance-dependence of the topographic effects on gust factors was revealed subsequently. Furthermore, the canyon effect was identified and discussed based on the observations of wind at a saddle point between two mountain peaks. This study aims to further understanding of the characteristics of surface wind over rugged terrain. The presented results are expected to be useful for structural design, prevention of pollutant dispersion, and validation of CFD (computational fluid dynamics) models or techniques over complex terrains.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.206-209
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• 2011

During landing approach, an airplane could experience dynamic unstable motion by the combination of a gust and elevator control to cancel the disturbances. This situation is dangerous and could lead to a loss of an airplane. In this paper, numerical analysis was used to study the effect of pitch oscillating 2-D high lift devices in a landing condition. Experimental data on a pitching naca0012 airfoil was used for code validation. Dynamic characteristics of an airfoil, single slotted flap for mid-class passenger aircraft were analyzed. Unsteady Navier-Stokes analysis was performed with Spalart-Allmaras turbulence model for separation dominant low speed flow. As a result, flow hysteresis of a flapped airfoil was more complex than that of an oscillating airfoil. So, dynamic analysis of a flap in a landing condition is very important for operational safety.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.113-113
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• 2000

A robust adaptive technique for the longitudinal control of a platoon of automated vehicles is presented. A nonlinear model is used to represent the vehicle dynamics of each vehicle within the platoon. The external disturbance such as wind gust and a disturbance term due to engine transmission variations and so on are considered. The state observer is used to avoid direct measurement of the relative velocity or acceleration between the controlled and leading vehicles or the controlled vehicle's acceleration. It is shown that platoon stability can be recovered in operation even if a speed dependent spacing policy is adopted, which incorporates a constant time headway in addition to the constant distance. The simulation results demonstrate excellent tracking even in the presence of disturbances.

• Wind and Structures
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• 제15권2호
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• pp.177-188
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• 2012

The meteorological events that cause most strong winds in Brazil are extra-tropical cyclones, downbursts and tornadoes. However, one hurricane formed off the coastline of southern Brazil in 2005, a tropical storm formed in 2010 and there are predictions that others may form again. Events such as those described in the paper and which have occurred before 1987, generate data for the wind map presented in the Brazilian wind loading code NBR-6123. This wind map presents the reference wind speeds based on 3-second gust wind speed at 10 m height in open terrain, with 50-year return period, varying from 30 m/s (north half of country) to 50 m/s (extreme south). There is not a separation of the type of climatological event which generated each registered velocity. Therefore, a thunderstorm (TS), an extra-tropical pressure system (EPS) or even a tropical cyclone (TC) are treated the same and its resulting velocities absorbed without differentiation. Since the flow fields generated by each type of meteorological event may be distinct, the indiscriminate combination of the highest wind velocities with aerodynamic coefficients from boundary layer wind tunnels may lead to erroneous loading in buildings.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.470-474
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• 2010

Various anti-scattering agents for suppression of dust scattering at waste depository were compared in this study. Based on the price, easy of usage, and no toxicity, 1% of $Al_2(SO_4)_3$ was selected as surface hardening agents. Only lower than 2% of total weight were flied when wind speed was monthly maximum velocity during 1 hr. These results were quite good with comparison of S anti-scattering agents which was made by C company in Korea. When $Al_2(SO_4)_3$ was spread, the surface waste became hard therefore the effect of suppression of scattering dust was long lasting. It was recommend that 2% of $Al_2(SO_4)_3$ was spread to keep suppression of scattering dust when sudden gust of wind such as natural disaster was occurred.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.414-419
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• 2006

The ballast or other objects may be located on the rail road by a lump of ice, repairing operation on the track, or the strong gust due to the high speed running of the train. When a train operated in this condition, it causes serious damages to the wheel, train, and structures near the track, or the secondary ballast flying. To remove these objects safely, a ballast blower is suggested which was attached under the train. Firstly, the numerical analyses are investigated to find out the basic flow characteristics of the ballast blower. Next, the performance of the ballast blower is verified by wind tunnel experiments. Through these studies, it is expected that the ballast blower can be applied practically.